Highest temperature in Tokyo on August 21?

Platform comparison

Market context

Tokyo's peak temperature on 21 August 2026 will be recorded at Haneda Airport Station and resolved against Weather Underground's Daily Observations table rather than the Day High & Low summary—a distinction that matters for automated resolution systems and API-based monitoring. The settlement window closes at midday UTC, creating a hard cutoff for intraday temperature movements that occur after local midnight.

Historical August temperatures at Haneda show a consistent pattern: daily highs typically range between 32–35°C during late summer, with occasional peaks above 36°C during heat waves. The 2023 August average high was 34.1°C; 2022 saw several days exceed 35°C. The 0% crowd probability suggests either extreme confidence in a specific temperature band or sparse liquidity in adjacent ranges. Traders building conditional orders should note that Haneda's sensor placement and urban heat island effects produce readings 1–2°C higher than suburban stations, making historical comparisons with broader Tokyo data unreliable for calibration.

Watch Japan Meteorological Agency forecasts released in early August 2026, particularly any alerts for high-pressure systems or typhoon remnants that could suppress temperatures. Programmatic traders should establish data feeds from Weather Underground's API well before settlement; the distinction between Daily Observations and Day High & Low tables requires parsing the correct endpoint. Haneda's hourly data becomes publicly available within hours of recording, enabling real-time position adjustments as the day progresses and afternoon peaks develop.

Methodology

We track Highest temperature in Tokyo on August 21? across the five venues with material prediction-market liquidity. The probability shown is the live Polymarket mid; the comparison rows summarise how each venue treats the underlying contract — fees, KYC thresholds, settlement currency, deposit options. The highlighted row marks the cheapest route into Polymarket's order book.

Resolution & payout

At resolution the UMA oracle takes over: a proposer posts the outcome with a bond, any token holder can dispute within two hours. Without dispute the result is accepted and the smart contract distributes USDC instantly.

On Kalshi (CFTC-regulated) resolution runs through their in-house clearing engine in USD. Betfair Exchange settles after match end in the account's local currency. Manifold pays no cash — only its in-platform "mana" currency.

UK Frequently Asked Questions

Where can I trade this market with the lowest fees?

Polymarket is geo-blocked in the US/UK/EU. The easiest 0%-fee broker into the same order book is Polymarket Review UK. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

How does resolution work?

Through the UMA Optimistic Oracle on Polygon: a proposer submits the outcome, a two-hour challenge window opens, and USDC payouts settle automatically once the result is final.

Is Polymarket legal in the UK?

Polymarket is accessible to UK traders but is not UKGC-licensed. It operates under US CFTC jurisdiction. UK residents face no domestic legal prohibition on using it, but UKGC consumer protections do not apply. For UKGC-regulated alternatives, Betfair Exchange and Smarkets offer similar prediction-style markets.

Do I pay tax on prediction market profits in the UK?

UKGC-licensed platform profits (Betfair, Smarkets) are typically tax-free gambling winnings for UK individuals. Polymarket profits involve USDC crypto transactions, which HMRC treats as Capital Gains Tax events. Keep full transaction records and report via Self Assessment if gains exceed £3,000 per tax year.

How do I deposit on Polymarket from the UK?

UK traders typically fund Polymarket via Coinbase UK, Kraken or Revolut — buying USDC with GBP and transferring to a Polygon-compatible wallet (MetaMask, Coinbase Wallet). Polymarket's onboarding walks you through the bridging process. Typical GBP-to-USDC conversion costs 0.5–1%.